This fixes a couple of bugs in the buffer handling in virtio-i2c which can result in incorrect data on the I2C bus or memory corruption in the guest. I tested this on UML (virtio-uml needs a bug fix too, I will sent that out later) with the device implementation in rust-vmm/vhost-device. Vincent Whitchurch (2): i2c: virtio: disable timeout handling i2c: virtio: fix completion handling drivers/i2c/busses/i2c-virtio.c | 46 ++++++++++++++------------------- 1 file changed, 19 insertions(+), 27 deletions(-) -- 2.28.0
Vincent Whitchurch
2021-Oct-19 07:46 UTC
[PATCH 1/2] i2c: virtio: disable timeout handling
If a timeout is hit, it can result is incorrect data on the I2C bus
and/or memory corruptions in the guest since the device can still be
operating on the buffers it was given while the guest has freed them.
Here is, for example, the start of a slub_debug splat which was
triggered on the next transfer after one transfer was forced to timeout
by setting a breakpoint in the backend (rust-vmm/vhost-device):
BUG kmalloc-1k (Not tainted): Poison overwritten
First byte 0x1 instead of 0x6b
Allocated in virtio_i2c_xfer+0x65/0x35c age=350 cpu=0 pid=29
__kmalloc+0xc2/0x1c9
virtio_i2c_xfer+0x65/0x35c
__i2c_transfer+0x429/0x57d
i2c_transfer+0x115/0x134
i2cdev_ioctl_rdwr+0x16a/0x1de
i2cdev_ioctl+0x247/0x2ed
vfs_ioctl+0x21/0x30
sys_ioctl+0xb18/0xb41
Freed in virtio_i2c_xfer+0x32e/0x35c age=244 cpu=0 pid=29
kfree+0x1bd/0x1cc
virtio_i2c_xfer+0x32e/0x35c
__i2c_transfer+0x429/0x57d
i2c_transfer+0x115/0x134
i2cdev_ioctl_rdwr+0x16a/0x1de
i2cdev_ioctl+0x247/0x2ed
vfs_ioctl+0x21/0x30
sys_ioctl+0xb18/0xb41
There is no simple fix for this (the driver would have to always create
bounce buffers and hold on to them until the device eventually returns
the buffers), so just disable the timeout support for now.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch at axis.com>
---
drivers/i2c/busses/i2c-virtio.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
index f10a603b13fb..7b2474e6876f 100644
--- a/drivers/i2c/busses/i2c-virtio.c
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -106,11 +106,10 @@ static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
static int virtio_i2c_complete_reqs(struct virtqueue *vq,
struct virtio_i2c_req *reqs,
- struct i2c_msg *msgs, int num,
- bool timedout)
+ struct i2c_msg *msgs, int num)
{
struct virtio_i2c_req *req;
- bool failed = timedout;
+ bool failed = false;
unsigned int len;
int i, j = 0;
@@ -132,7 +131,7 @@ static int virtio_i2c_complete_reqs(struct virtqueue *vq,
j++;
}
- return timedout ? -ETIMEDOUT : j;
+ return j;
}
static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
@@ -141,7 +140,6 @@ static int virtio_i2c_xfer(struct i2c_adapter *adap, struct
i2c_msg *msgs,
struct virtio_i2c *vi = i2c_get_adapdata(adap);
struct virtqueue *vq = vi->vq;
struct virtio_i2c_req *reqs;
- unsigned long time_left;
int count;
reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
@@ -164,11 +162,9 @@ static int virtio_i2c_xfer(struct i2c_adapter *adap, struct
i2c_msg *msgs,
reinit_completion(&vi->completion);
virtqueue_kick(vq);
- time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
- if (!time_left)
- dev_err(&adap->dev, "virtio i2c backend timeout.\n");
+ wait_for_completion(&vi->completion);
- count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left);
+ count = virtio_i2c_complete_reqs(vq, reqs, msgs, count);
err_free:
kfree(reqs);
--
2.28.0
The driver currently assumes that the notify callback is only received
when the device is done with all the queued buffers.
However, this is not true, since the notify callback could be called
without any of the queued buffers being completed (for example, with
virtio-pci and shared interrupts) or with only some of the buffers being
completed (since the driver makes them available to the device in
multiple separate virtqueue_add_sgs() calls).
This can lead to incorrect data on the I2C bus or memory corruption in
the guest if the device operates on buffers which are have been freed by
the driver. (The WARN_ON in the driver is also triggered.)
BUG kmalloc-128 (Tainted: G W ): Poison overwritten
First byte 0x0 instead of 0x6b
Allocated in i2cdev_ioctl_rdwr+0x9d/0x1de age=243 cpu=0 pid=28
memdup_user+0x2e/0xbd
i2cdev_ioctl_rdwr+0x9d/0x1de
i2cdev_ioctl+0x247/0x2ed
vfs_ioctl+0x21/0x30
sys_ioctl+0xb18/0xb41
Freed in i2cdev_ioctl_rdwr+0x1bb/0x1de age=68 cpu=0 pid=28
kfree+0x1bd/0x1cc
i2cdev_ioctl_rdwr+0x1bb/0x1de
i2cdev_ioctl+0x247/0x2ed
vfs_ioctl+0x21/0x30
sys_ioctl+0xb18/0xb41
Fix this by calling virtio_get_buf() from the notify handler like other
virtio drivers and by actually waiting for all the buffers to be
completed.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch at axis.com>
---
drivers/i2c/busses/i2c-virtio.c | 34 +++++++++++++++------------------
1 file changed, 15 insertions(+), 19 deletions(-)
diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
index 7b2474e6876f..2d3ae8e238ec 100644
--- a/drivers/i2c/busses/i2c-virtio.c
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -22,24 +22,24 @@
/**
* struct virtio_i2c - virtio I2C data
* @vdev: virtio device for this controller
- * @completion: completion of virtio I2C message
* @adap: I2C adapter for this controller
* @vq: the virtio virtqueue for communication
*/
struct virtio_i2c {
struct virtio_device *vdev;
- struct completion completion;
struct i2c_adapter adap;
struct virtqueue *vq;
};
/**
* struct virtio_i2c_req - the virtio I2C request structure
+ * @completion: completion of virtio I2C message
* @out_hdr: the OUT header of the virtio I2C message
* @buf: the buffer into which data is read, or from which it's written
* @in_hdr: the IN header of the virtio I2C message
*/
struct virtio_i2c_req {
+ struct completion completion;
struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned;
uint8_t *buf ____cacheline_aligned;
struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned;
@@ -47,9 +47,11 @@ struct virtio_i2c_req {
static void virtio_i2c_msg_done(struct virtqueue *vq)
{
- struct virtio_i2c *vi = vq->vdev->priv;
+ struct virtio_i2c_req *req;
+ unsigned int len;
- complete(&vi->completion);
+ while ((req = virtqueue_get_buf(vq, &len)))
+ complete(&req->completion);
}
static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
@@ -69,6 +71,8 @@ static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
if (!msgs[i].len)
break;
+ init_completion(&reqs[i].completion);
+
/*
* Only 7-bit mode supported for this moment. For the address
* format, Please check the Virtio I2C Specification.
@@ -108,21 +112,13 @@ static int virtio_i2c_complete_reqs(struct virtqueue *vq,
struct virtio_i2c_req *reqs,
struct i2c_msg *msgs, int num)
{
- struct virtio_i2c_req *req;
bool failed = false;
- unsigned int len;
int i, j = 0;
for (i = 0; i < num; i++) {
- /* Detach the ith request from the vq */
- req = virtqueue_get_buf(vq, &len);
+ struct virtio_i2c_req *req = &reqs[i];
- /*
- * Condition req == &reqs[i] should always meet since we have
- * total num requests in the vq. reqs[i] can never be NULL here.
- */
- if (!failed && (WARN_ON(req != &reqs[i]) ||
- req->in_hdr.status != VIRTIO_I2C_MSG_OK))
+ if (!failed && req->in_hdr.status != VIRTIO_I2C_MSG_OK)
failed = true;
i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
@@ -158,11 +154,13 @@ static int virtio_i2c_xfer(struct i2c_adapter *adap,
struct i2c_msg *msgs,
* remote here to clear the virtqueue, so we can try another set of
* messages later on.
*/
-
- reinit_completion(&vi->completion);
virtqueue_kick(vq);
- wait_for_completion(&vi->completion);
+ /*
+ * We only need to wait for the last one since the device is required
+ * to complete requests in order.
+ */
+ wait_for_completion(&reqs[count - 1].completion);
count = virtio_i2c_complete_reqs(vq, reqs, msgs, count);
@@ -211,8 +209,6 @@ static int virtio_i2c_probe(struct virtio_device *vdev)
vdev->priv = vi;
vi->vdev = vdev;
- init_completion(&vi->completion);
-
ret = virtio_i2c_setup_vqs(vi);
if (ret)
return ret;
--
2.28.0
On 19-10-21, 09:46, Vincent Whitchurch wrote:> The driver currently assumes that the notify callback is only received > when the device is done with all the queued buffers. > > However, this is not true, since the notify callback could be called > without any of the queued buffers being completed (for example, with > virtio-pci and shared interrupts) or with only some of the buffers being > completed (since the driver makes them available to the device in > multiple separate virtqueue_add_sgs() calls). > > This can lead to incorrect data on the I2C bus or memory corruption in > the guest if the device operates on buffers which are have been freed by > the driver. (The WARN_ON in the driver is also triggered.) > > BUG kmalloc-128 (Tainted: G W ): Poison overwritten > First byte 0x0 instead of 0x6b > Allocated in i2cdev_ioctl_rdwr+0x9d/0x1de age=243 cpu=0 pid=28 > memdup_user+0x2e/0xbd > i2cdev_ioctl_rdwr+0x9d/0x1de > i2cdev_ioctl+0x247/0x2ed > vfs_ioctl+0x21/0x30 > sys_ioctl+0xb18/0xb41 > Freed in i2cdev_ioctl_rdwr+0x1bb/0x1de age=68 cpu=0 pid=28 > kfree+0x1bd/0x1cc > i2cdev_ioctl_rdwr+0x1bb/0x1de > i2cdev_ioctl+0x247/0x2ed > vfs_ioctl+0x21/0x30 > sys_ioctl+0xb18/0xb41 > > Fix this by calling virtio_get_buf() from the notify handler like other > virtio drivers and by actually waiting for all the buffers to be > completed. >Add a fixes tag here please, so it can get picked to the buggy kernel version as well.> Signed-off-by: Vincent Whitchurch <vincent.whitchurch at axis.com>Acked-by: Viresh Kumar <viresh.kumar at linaro.org> -- viresh